I had a similar problem (the test tubes from the hobby store didn't fit my simants nest) this is how I solved it:

Put tubing in the hole, then push the test tube over the free tubing. If the difference in diameter is small enough it holds fine (for me it was 14mm tubing and a 15mm test tube).
Obviously that only works with large ants like Camponotus or Formica - smaller Solenopsis, Myrmica, Lasius or Nylanderia would just walk out of the setup due to the gap.

"We should respect all forms of consciousness. The body is just a vessel, a mere hull."

I recently purchased two hybrid nests.
The problem is the supplied test tubes don't fit the holes very well

One nest has two holes that will hold it, two that doesn't hold them at all.
The other nest only has one hole that will hold the test tube... The rest are too loose or too tight.

And the tubing that came with the nests doesn't fit any of the holes.

The AC Test Tube Portal I ordered holds the test tubes perfectly so I don't think there is anything wrong with the tubes.

Any Ideas?

This is odd. We have not had anyone else mention that they were having problems with test tube and poly tubing fitting properly. Not sure what could have happened. You know the poly tubing fits deeper into the entrance holes of the Hybrid right?